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DNA contested in rape trial

Lawyers square off over test results

Posted: January 27, 2009 9:18 p.m.
Updated: January 28, 2009 4:55 a.m.
 

SAN FERNANDO - Lawyers squared off over the accuracy of DNA evidence as the prosecution continued its case against the alleged Canyon Country rapist Tuesday.

Los Angeles County District Attorney Angela Jordan called DNA expert Lori Schumann to the stand Tuesday morning to testify against alleged knife-point rapist Adrian Arriano.

Schumann, an L.A. County Sheriff's Scientific Services senior criminalist, gave expert testimony on DNA samples collected from two unidentified victims and Arriano in 2007.

Jordan fired questions at Schumann and attempted to tie Arriano to the physical evidence.

"The reference sample taken from Adrian Arriano matched (Arriano) in the Addie T. and Sheri C cases," Schumann said. Addie T and Sheri C. are aliases given to two victims in the rape trial.

A statistical analyses awed the prosecution.

"There is a 1 in 248 quintillion chance this is someone besides Arriano," Schumann said.

Jordan asked Schumann to quantify that number.

"That's 248 with 18 zeros behind it. A statistical analysis is there to demonstrate the rarity of the DNA profile," Schumann said.

Arriano's defense attorney Julia Knox wasn't awed by Schumann's testimony and spent Tuesday afternoon poking holes in the expert witness' claims.

Deputies collected DNA from the genitals and the bodies of two victims and from Arriano. Evidence was also collected from one victim's carpet. In each case, the crime lab determined Arriano's DNA profile was either a major contributor, or a likely contributor, to the sample.

Knox asked Schumann whether the DNA replicating process could be flawed.

DNA evidence is replicated so criminalists have enough samples to analyze, Schumann said.

The process duplicates the DNA samples, but isn't 100-percent efficient, she said.

"Does that mean (the process) isn't 100 percent accurate?" Knox asked.

"That's correct," Schumann said.

An allele is a genetic fingerprint used by criminalists to match suspects to crimes, Schumann said.
One sample analyzed by the crime lab in the Arriano case showed three separate alleles, or genetic fingerprints.

Knox alleged the third genetic fingerprint could belong to another person or shows possible sample contamination.

"That's a possibility," Schumann said to Knox inquiries about the third DNA marker.

However, there is a scientific explanation for the third marker.

"DNA samples are like long sentences and the alleles are like words that are repeated in the sentence," Schumann said.

The third genetic finger is like a stutter in the sentence that shows up during a computer analysis.
Schumann didn't initially identify the third genetic fingerprint as a stutter.

"It was in the stutter position, but it was so close to the next allele that I identified it as an inconclusive allele," she said.

Knox asked what Schuman's basis for identifying the third genetic fingerprint as inconclusive.
"That comes from training and experience," Schumann said.

Jordan tried to restore the expert witness' credibility on redirect.

"You were asked a lot of questions about ifs. But in this case, was there evidence of contamination? In this case, was there evidence of degradation?" Jordan asked.

"No," Schumann said.

Jordan pressed Schumann on whether the existence of a third genetic fingerprint in the stutter position invalidates the sample.

"No," Schumann said.

Jordan also asked whether the PCR process is the standard in the scientific community.

Schumann said yes.

After Arriano's state case ends and he serves any associated jail time, a federal deportation case looms. Arriano allegedly illegally crossed the U.S.-Mexico border three times.

He was deported twice.

"Illegal re-entry is the top prosecuted crime by the U.S. Attorney's Los Angeles office," said Thom Mrozek, office spokesman.

Of the 1,900 prosecutions by the Los Angeles office in 2007, more than one-third were for illegal re-entry into the United States.

"These are individuals with at least one illegal re-entry who have also committed a crime in the country," he said.

Before the U.S. Attorney's Office prosecutes an illegal re-entry case, Immigration and Customs Enforcement conducts an administrative hearing, ICE spokeswoman Virginia Kice said.

During the administrative hearing, ICE determines whether to deport the person or hand him or her over to the U.S. Attorney's Office for an illegal re-entry hearing, she said.

The penalty for illegal re-entry is up to 20 years in prison, and defendants serve 85 percent of their sentence under federal sentencing guidelines, Kice said.

"We are trying to discourage people from coming back and keep them off the streets," she said.

Arriano will go through an ICE hearing and potentially an illegal re-entry hearing once his California trial is complete, Mrozek said.

Arriano's state rape trial resumes today at 11 a.m. in San Fernando Superior Court.

The district attorney charged Arriano with 29 counts including one count of attempted murder, 10 counts of forcible rape, five counts of sexual penetration by a foreign object, three counts of sodomy, three counts of forced oral copulation, four counts of burglary, one count of false imprisonment by violence, one count of residential robbery and one count of assault to commit a felony during a burglary.

Santa Clarita Valley Sheriff's Station's deputies allege Arriano broke into the homes of victims before raping them at knife-point.

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